Question

我想在创建活动时更改TextViews值。

在LoginActivity上，我使用：

开始我的活动

startActivity(new Intent(LoginActivity.this, MainActivity.class));

但我不知道在哪里放置代码来更改我的textviews值。

当我把它放在onCreate上时，我的应用程序就崩溃了......

我的logcat没有工作，所以我看不到我的异常...

但是在做

时崩溃了

    TextView t = (TextView) findViewById(R.id.zanuka_username);
    t.setText("lllll");

的onCreate

 @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        TextView t = (TextView) findViewById(R.id.zanuka_username);
        t.setText("lllll");

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

       /** FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });
        **/

        //ImageView profilePicture = (ImageView)findViewById(R.id.zanuka_profilepicture);
        //new ImageLoadTask("http://chat.keecode.net/account/picture/1", profilePicture).execute();

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
                this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.setDrawerListener(toggle);
        toggle.syncState();

        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);
    }

Answer 1

你得到了这个例外：

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference

告诉您TextView t为NULL。原因是您的activity_main.xml中缺少带有id =“zanuka_username”的TextView。

Answer 2

TextView mTextView;
@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main_activity);
        mTextView = (TextView)findViewById(R.id.your_text_view);
        mTextView.setText("Main activity created");
    }

Answer 3

请发布您的MainActivity oncreate代码和您获得的例外

这应该有效

TextView tv = (TextView)findViewById(R.id.tv);
tv.setText("Hello World");

在你的onCreate中。

更改活动创建时的TextView值

3 个答案: